TAKING IT SLOW: Jon Niese, who is working on a change-up during spring training, threw two no-hit innings yesterday vs. the Marlins. (AP)

JUPITER, Fla. — Jon Niese could use a change in his life beyond his new nose.

The Mets lefty has a mission this spring: Develop a change-up, as a legitimate fourth pitch to complement his fastball, cutter and curve. Pitching coach Dan Warthen has made the change-up a non-negotiable item on Niese’s agenda.

“Any left-hander who doesn’t have a change-up is not a wise man,” Warthen said yesterday.

Niese began working on the pitch near the end of last season, and ideally would like to throw it around 80 mph — about 10-12 mph slower than his fastball. He threw several change-ups in his two shutout innings yesterday against the Marlins in which he did not allow a hit and walked one with two strikeouts.

It comes after Niese had surgery this offseason, at the urging of former teammate Carlos Beltran, to change the shape of his nose. But during the process Niese was also told he had an irregularity in his sinus that was affecting his breathing. The problem was corrected, and Niese has credited that with improved breathing during workouts.

Last year Niese threw a change-up 5.1 percent of the time, according to fangraphs.com. The Mets don’t have a percentage in mind for this year, but just want the change-up to become a more prominent part of his arsenal.

“That’s the pitch I have less experience with, so I’m definitely going to be working on that a lot more, just so I can master it like I have with my cutter,” Niese said. “My cutter was a real good pitch for me last year. I think the change-up could even be more devastating if I master it.”

Niese doesn’t need to go far if he seeks advice on the pitch — Johan Santana has built a career based on his mastery of the change-up. But Niese says he needs less advice than practice, since the change-up is such a difficult pitch to throw.

“It’s all feel, because you’re gripping the ball in such an awkward way,” Niese said. “It takes years and years of practice just to get the feel for it. Some people can do it, some people can’t. [Santana] is just really good at it.

“It’s definitely not going to be Johan’s change-up, obviously. That’s just something you can’t duplicate, but as long as I can get it better, I think it can be a good pitch for me.”

Warthen has given Niese the leeway this spring to make as many mistakes as he pleases trying to further develop his change-up.

“In spring training he can get hurt with it as much as he wants — as long as he uses it,” Warthen said. “If he gets comfort and confidence with that particular pitch, it’s going to help him get through games with a lot fewer pitches.”

And fewer pitches leads into the Mets’ other mandate with Niese

this spring: Don’t nibble ahead in the count.

“When he pounds the strike zone, he gets easy outs,” manager Terry Collins said. “If you can locate your fastball like Jon can, and you’ve got a change to go with it, you’re going to be pretty effective.”

Niese was critical of himself for walking Donnie Murphy with two outs in the second inning after getting ahead in the count in yesterday’s 7-0 exhibition win over the Marlins.

“The moral of that is pound the zone and get early outs,” Niese said. “That’s a great philosophy of pitching. Obviously there’s going to be situations where you want to throw a ball on purpose, but as long as it’s with purpose, it’s a good pitch.”